Digestive System — Breaking Down Food

Pathway: Mouth → Esophagus → Stomach → Small intestine (duodenum, jejunum, ileum) → Large intestine → Rectum → Anus

Digestion by organ:

Mouth — mechanical digestion; salivary amylase begins starch digestion

Stomach — pepsin (protein digestion); HCl (pH 1.5–3.5); churning

Small intestine — primary absorption site; pancreatic enzymes (proteases, lipase, amylase); bile from liver emulsifies fats; brush border enzymes

Large intestine — water reabsorption; gut bacteria; no significant digestion

Pancreatic secretions:

Bicarbonate (neutralizes stomach acid)

Trypsin, chymotrypsin (proteins); secreted as zymogens

Lipase (fats); Amylase (carbs)

Absorption mechanisms:

Glucose/amino acids — secondary active transport (co-transport with Na⁺)

Fats — emulsified by bile → micelles → absorbed → chylomicrons → lymphatics

Vitamins — fat-soluble (A,D,E,K) absorbed with fats; water-soluble (B,C) by facilitated diffusion

Reference:

Wikipedia: Digestive System

https://en.wikipedia.org/wiki/Human_digestive_system